Passage Summary: A columnist adds up two different causes of bike accidents (bad behavior and bad gear), each over 25%, to conclude that bikers are responsible for over half of all accidents.

Conclusion: Bicyclists are at least partially responsible for more than 50 percent of bicycle-involved traffic accidents.

Reasoning: Rule-breaking by cyclists is a factor in over 25 percent of accidents, and poor equipment is a factor in over 25 percent of accidents.

Analysis: The columnist is making a classic mathematical error by assuming the two groups of accidents are mutually exclusive. If many accidents involve *both* a rule violation and bad equipment, you can't simply add the percentages together to get a total. For example, if the same 26% of accidents had both factors, the total 'biker-responsible' accidents would still only be 26%. Look for an answer that points out the failure to consider that these two categories might overlap.